Automatic reclosing-circuit-breaker system



April 7, 1931. R. A. FULLER 1,800,014

AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed May 1, 1929 Inventor:

\ Roger A. FIJI ler",

His Atiorneg.

Patented Apr. 7, 1931 UNITED STATES ROGER A. FULLER,

PATENT OFFICE OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO GENERAL ELEC- TRICCOMPANY, A CORPORATION OF NEW YORK AUTOMATIC RECLOSING-CIBCUIT-BREAKEB SYSTEM Application filed May 1, 1929. Serial No. 358,664.

My invention relates to automatic reclosing circuit breaker systems and particularly to systems of the type disclosed and claimed in Letters Patent 1,626,495, issued to Arvid E. Anderson, assignor to the assignee of this application. y

In the arrangement disclosed in said Letters Patent a load indicating resistor is arranged to be connected in series between a supply circuit and a load circuit when the circuit breaker connecting the two circuits is open. When the load circuit is energized at some other point while the circuit breaker is open, the reclosing of the circuit breaker is controlled in response to the difference between the voltages of the two circuits. When, however, the load circuit is not energized at some other other point while the circuit breaker is open, the reclosing of the circuit breaker is controlled by means of a reclosing relay which has a winding which is energized in response to the voltage drop produced across the load circuit by the current supplied thereto through the load indicating resistor. In order to render this reclosing relay operative to control the reclosing of the circuit breaker when the load circuit is not energized at some otherpoint, a selective relay is provided which is connected so that it is energized in response to the voltage drop across theload indicating resistor and which is arranged to render the reclosing relay operative to control the reclosing when the voltage drop acrossthe load indicating reslstor is above a predetermined value.

It has been found in practice that when the arrangement disclosed in the above-mentioned Letters Patent is used in some systems,'conditions may occur under which it is desirable to reclose the circuit breaker when the load circuit is not energized at some other point and the resistanceof the load connected to the load circuit is so high relative to the resistance of the load indicating resistor that the voltage drop across the load indicating resistor is not sufiicient to cause the selective relay to render the reclosing relay operative to respond to the voltage across the load circuit but is suiiicient to prevent the other reclosing means from reclosing the circuit breaker and one object of my invention is to provide an improvement of the arrangement disclosed in the above-mentioned Letters Patent whereby the circuit breaker can be reclosed under such high resistance load conditions.

My invention will be better understood from the following description when taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the accompanying drawing which diagrammatically shows an automatic reclosing circuit breaker system embodying my invention, 1 is a supply circuit, which is arranged to be connects to a load circuit 2 by means of a circuit breaker 3 which may be of any suitable type, examples of which are well known in the art. The load circuit 2 v is arranged to be supplied by other sources of current (not shown).

As shown in the drawing the circuit breaker 3 is of the well known contactor type and is provided with a closing coil 4 which, when energized, maintains the circuit breaker closed. The circuit of the closing coil 4 is controlled by an overload responsive device 5 which is arranged in any suitable manner, examples of which are well known in the art, so as to effect the deenergization of the closing coil 4 and the opening of the circuit breaker 3 upon the occurrenceof predetermined abnormal load conditions. As shown in the drawing the overload responsive device 5 is an overcurrent relay whose coil is connected so as to be energized in accordance with the current flowing through the circuit breaker 3. The relay 5 is arranged to open its contacts 6 in the circuit of the closing coil 4 when the current flowing through the circuit break- I cuit breaker in response to the relative pot'entials of the supply circuit 1 and the load circuit 2 when the load circuit is energized at same other point. As shown in the drawing, the relay 8 is connected across the main terminals of the circuit breaker 3 so that it is energized in response to the difference between the voltages of the supply circuit 1 and the load circuit 2, and is arranged to complete an energizingcircuit for the closing coil 4 when the voltage difference is less than'a PTO? determined amount. 3

In order to control the selective operation of the reclosing relays 7 and 8 so that the relay 7 is operative to reclose the circuit breaker only when the load circuit is not energized at some other point, a relative high resistance selective relay v9 is provided which is respon sive to the diiierence between the voltages of the supply circuitl and the load circuit 2. This voltage difference when the circuit breaker 3 is open is an indication of the condition of the load circuit 2. If no other source is connected to the load circuit 2 the-Voltage difference is substantially equal to the voltage of the supply circuit 1, whereas if the load circuit is energized by some other source when the circuit breaker 3 is'open, the voltage diilerence'is considerably less than the source voltage. I use this difference between the Voltages as a means of determining whether the reclosing ofthe circuit breaker shall be efiective by the relay 7 or the relay 8 by designing the selective relay 9 so that it renders the relay 7 operative to control the reclosing only when the voltage difference is above a predetermined value, which is so great that it only occurs wheuthe load circuit is not energized by some other source.

The reclosing relay 7, which is arranged to respond to the voltage of the load circuit 2, maybe of any suitable type, example of which are well known in the art. As shown in the drawing, the relay 7 is of the well known polarized type comprising a polarized winding 10 which is arranged to be connected across the source 1 by the selective relay 9 and time relay 17 and an operating winding 11 which is connected across the load circuit 2 permanently. When both of its windings are energized the relay 7 is arranged to close its contacts 13 in an'energizing circuit for the closing coil 4 when the voltage across the load circuit exceeds apredetermined value;

' In'order to obtain an indication of the load condition of the load circuit 'whenthecircuit breaker 3 is open and no other source is connected to the load circuit, a load indicating resistor 14 is arranged to be connected" in series with the source 1' and the load circuit 2under such conditions. In accordance with my invention the selective relay 9, in addition to rendering the reclosing relay 7 operative to control the reclosing of the circuit breaker 3 by connecting the magnetizing winding 10 across the supply circuit 1 also controls the connections of the load indicating resistor 14 so that it is connected in series between the supply circuit 1 and the load circuit 2 only when the circuit breaker 3 is open and the load circuit is not energized by some other source. The resistances of the. windings of the relays 8 and 9, which are connected directly across the terminals of the circuit breaker 3, are relatively high with respect to the re sistance of the load indicating resistor 14. Therefore, when only the relays 8 and 9 are connected in series between the supply and load circuit, the relay 9 is arranged to close 7 its contacts over a much greater range of load resistance than when the relatively low resistance of the load indicating resistor 14 is also connected in series between the two cir cuits. For example, assume. ror the purpose of illustration that the equivalent resistance of the two windings of relays 8 and 9 is fifty times the equivalent resistance of the two windings and the resistor 14 and that relay 9 is arranged to close its contacts '23 in response to 50% of normal voltage. Under the conditions assumed the range of load resistance over which the relay 9 can close its contacts 23 when the resistor 14 is not connected in circuit is fifty times greater than the range over which the relay can close its contacts 23 when the resistor 14 is connected in circuit. Therefore, when the current breaker 3 is open, the load circuit 2 is not energized by some other source, and the load resistance is very high the. voltageimpressed across the winding of the selective relay 9 is still great enough to effect the operation thereof so" as to render'the reclosing relay 7 operative to reclosethe circuit breaker. As shown in the drawing, the selective relay 9 when the voltage difference bewith my improved arrangement, 7

tween the supply circuit 1 and the load cir- I cuit2 is above apredetermined value, completes an energizing circuit fora control relay 15 which'when energized connects the load indicating resistor 14 in series between the supply circuit and the load circuit 2, so that a small current is supplied to the load circuitto energize the 'operating winding 11 of the reclosing relay 7.

It is desirable to delay the reclosing of the circuit breaker 3 for a predetermined time after it has been opened by an abnormal load on the load circuit 2. V Foraccomplishing this:

result I provide a time relay 17 with contacts 18 which are connected in the energizing circuitsof the closing coil 4, the polarizing winding 10 of the relay 7 and the winding of the control relay 15 so that these windings can be energized only when the contacts 18 are closed. The time relay 17is arranged to be energized in response to the opening of the circuit breaker 3 and is arranged in any suitable manner, examples of which are well known in the art, so thatit does not close its supplied with contacts 18 until after the relay has been energized for a certain length of time.

The operation of the arrangement shown in the drawing is as follows When the circuit breaker 3 is closed and the current through the circuit breaker is less than a predetermined value, a circuit for the closing coil 4 is maintained from one side of the supply circuit 1 through auxiliary contacts 20 on thecircuit breaker 3, contacts 6 of overload relay 5, closing coil 4 to the other side of the supply circuit.

hen an overload occurs so that overload relay operates and opens its contacts 6, the above traced circuit for the closing coil 4 is opened and the circuit breaker 3 opens.

The opening of the circuit breaker 3 disconnects the supply circuit 1 from the load circuit 2 so that the voltage of the abnormal load circuit 2 decreases to a value which causes the reclosing relay 7 to open its contacts 13 if they are closed during the normal operation of the arrangement. The relay 7 may be arranged so that after it has closed its contacts 13 the operating winding 11, when it has substantially normal voltage impressed thereon, may maintain the relay contacts 13 closed.

The closing of the auxiliary contacts 21 on the circuit breaker 3 when it opens, completes an energizing circuit for the time relay 17 and after the relay has been energized for a predetermined length of time it closes its contacts 18. After the circuit breaker 3 opens, the relays 8 and 9 are energized in response to the difierence between the voltages of the supply circuit 1 and the load circuit 2; If the load circuit is not energized at some other point, the voltage difference between the supply and load circuits is suflicientto'cause the relay 8 to open its contacts 22 and to cause the relay 9 to close its contacts 23.- If, however, the load circuit is energized at some other point, the voltage difference is sufficient only to cause therelay 8 to open its contacts It will be assumed first that when the circuit breaker 3 opens, the load circuit 2 is not current from some other source. Under these conditions the relay 9 closes its contacts 23 and the relay 8 opens its contacts 22. As soon as the time relay 17 has closed its contacts 18 and the selective relay 9 has closed its contacts 23, an energizing circuit is completed across the supply circuit 1 for the magnetizing winding 10 of the re closing relay 7 so as to render the rcclc-sing relay operative to control the reclosing of the circuit breaker 3 in response to the resistance of the load connected across the load circuit 2. The closing of the contacts 18 of the relay 17 andthe contacts 23 of the selective relay 9 also completes across the supply circuit 1 an energizing circuit for the control relay 15. The energizing circuits for the winding 10 and the relay also include the auxiliary contacts 21 on the circuit breaker 3. The control relay 15 by closing its contacts 24 and connects the load indicating resistor 14 in series between the supply circuit 1 and the load circuit 2. A small current is, therefore, supplied to the load circuit through the load indicating resistor 14 and this small current produces a voltage drop across the load circuit which varies directly with the resistance of the load. In order to prevent the relay 9 from opening its contacts 23 as soon as the resistor 24 is connected in shunt with the relay winding, the relay 9 is provided with suit.- able timing means 26 examples of which are well known in the art, for preventing the relay from opening its contacts 23 for a predetermined time after the voltage difference decreases below a predetermined value.

When the load resistance increases to a predetermined value, the "oltage impressed upon the operating winding 11 of the reclosing relay 7 increases toa value suificient to cause the relay 7 to close its contacts 13. Vhen these contacts 13 close, an energizing circuit is completed for the closing coil 4 of the circuit breaker 3. This energizing circuit also includes the contacts 18 of the time relay 17, contacts 23 of the selective relay 9 and the contacts 6 of the overload relay 5.

The circuit breaker 3 by closing its auxiliary contacts 20 completes a holding circuit for its closing coil 4 which is independent of the contacts 13, 18 and 23 so that the circuit breaker 3 is not opened in response to the subsequent deenergization of the relays 9 and 17. The circuit breaker 3 by opening its auxiliary contacts 21 effects the deenergization of the time relay 17, the magnetizing winding 10 of the relay 7 and the control relay 15 and by closing its main contacts short circuits the reclosing relay 8 and the selective relay 9 so that the various devices are restored to their normal posit-ions.

It will now be assumed that when the circuit breaker 3 opens, the load circuit 2 is supplied with current from some other source. Under these conditions the voltage difference between the supply circuit 1 and the load circuit 2, after the circuit breaker 3 opens, is not suflicient to cause the selective relay 9 to close its contacts 23 but may be sufficient to cause the 'reclosing relay 8 to open its contacts 22. The circuit breaker 3 remains open until the time relay 17 closes its contacts 18 and the-voltage difference bet-we n the supply circuit 1 and the load circuit 2 is below a predetermined value when the contacts 22 of reclosing relay 8 are closed completing an energizing circuit for the closing coil 4. This energizing circuit also includes the contacts 18 of the time relay 17 and the contacts 6 of the overload relay 5. lVhen the circuit breaker 3 closes, it completes its heretofore described holding circuit so that it remains closed when thetime relay 71 7 and the reclosing relay 8 are restored to their normal positions in the manner above described.

"While I have, in accordance with the patent statutes, shown and described my invention as appliedto a particular system and as embodying various devicesdiagrammatically indicated, changes and modifications will be obvious to those skilled in the art and I, therefore, aim in the appended claims to cover all such changes and modifications as fall-within the true spirit and scope of my invention. :WhatI claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a supply circuit, a load circuit, a circuit breaker connecting said circuits, overload responsive means for effecting the opening of said circuit breaker, means for reclosing-said circuit breaker when said circuit breaker is open and said load circuit is energized independently of said supply circuit, means for'reclosing said circuit breaker in response to the voltage across said load circuit when said circuit breaker is open and said. load circuit is energized only by said supply circuit including a reclosing relay, current limiting means, and means responsive to the relative voltages of said circuits for efiectingthe connection of said current limit ing means in series with said circuits and for controlling the energization of said relay so that it is operative to'reclose said circuit breaker inresponse to the voltage across said load circuit. 7

2. In combination, a supply circuit, a load c'ircuit,-a circuit breaker connecting said circuits, overload responsive means for effecting the opening of said circuit breaker, means responsive to the relative voltages of said cir-.

cuits for reclosing said circuit breaker when it is open and said load circuit is energized independently of said supply circuit, means for reclosing said circuit breaker in response to the load impedance of said loadcircuit when said circuit breaker is open and" said load circuit is energized only by said supply circuit, current limiting means, and means controlled by the voltage of said load circuit for. connecting said current limiting means 7 in series between said circuitsjand for rendering said last mentioned reclosing means operative to ,reclose Ysaid circuit breaker when said load circuit is' not energized by some other supplycircuit-and said circuit breaker is open.

.. 3. In combinatiom'a supply circuit, a load i circuit, a'circuit breaker connecting said circuits, overload responsive means for opening saidcircuit breaker, reclosing means including means responsive to the difference between the voltages of said circuits for reclosing said circuit breaker when the voltage difference is below a predetermined value, reclosing means for said circuit breaker including a relay having a'WIIIClIIlg energized in response to the voltage across one of said circuits, a resistor, and means responsive to the difference between the voltages of said circuits foref'tecting the connection of said resistor in series with said circuits 'and'the connection of said relay winding across said one of said circuits when the voltage difference exceeds a predetermined value.

4. In combination, a supply circuit, a load circuit, a circuit breaker connecting said circuits, overload responsive means for opening said circuit breaker, reclosing means including means responsive to the difference be- 7 tween the voltages of said circuits for reclosing said circuit breaker when the voltage difference is below ,a predetermined value, and reclosing means for said circuit breaker including a relay having an operating winding, a resistor, electro-responsive means arranged when energized to effect the connection of said resistor in series with said circuits, means responsive to the voltage differencebetween said circuits for effecting the energization of said. electro-responsive means and of said operating winding when the voltage difierence exceeds a predetermined value,

and means for preventing said last mentioned voltage difference responsive means from effecting the deenergization of said electroresponsive means and of said relay winding for a predetermined time when the voltage difference subsequently decreases below a predetermined value. v

5. In an automatic reclosing circuit breaker system, two electric circuits, a-circuit breaker interconnecting said circuits, means for opening said circuit breaker, current limiting means, means responsive to the voltage'difference between said circuits when said circuit breaker isopenforeftecting the connection of said current limiting meansin series between said circuits and means controlled by the current supplied through said current limiting means forefiecting the reolosing of said circuit breaker.

6. In an automatic reclosing circuit breaker system, two electric circuits, a circuit'breaker I interconnecting said circuits, means for opening said circuit breaker, current limiting means, means responsive to the voltage difference between said circuits when said cir-V cuit breaker is open for effecting the connection ofsaid current limiting meansin series between said circuits, and means controlled by the voltage drop produced across one of said circuits by the current supplied thereto through said currentlimiting means for re closing said circuit breaker." Y

7. In combination, a supply circuit, a load circuit, a circ'uit breaker connecting said circuits, overload responsive means for effecting the opening of said circuit-breaker, means responsive to the voltage across said load circu t forreclosing said circuit breaker, current limiting means, and means responsive to the relative voltages across said circuits when said circuit breaker is open for effecting the connection of said current limiting means in series with said circuits.

8. In combination, a supply circuit, a load circuit, a circuit breaker connecting said circuits, overload responsive means for effecting the opening of said circuit breaker, reclosing means for controlling the reclosing of said circuit breaker in accordance with the impedance of the load connected to said load circuit, current limiting means, and means responsive to the relative voltages across said circuits when said circuit breaker is open for effecting the connection of said current limit ing means in series with said circuit and for rendering said reclosin means operative to reclose said circuit brea er.

In witness whereof, I have hereunto set my hand this 27th day of April, 1929.

ROGER A. FULLER. 

